The Silent Culprit: Paroxysmal Nocturnal Hemoglobinuria Masquerading as Cryptogenic Stroke

We present a case of a previously healthy 20-year-old male patient who experienced recurrent arterial thromboembolic events without identifiable risk factors. Extensive evaluation ultimately revealed paroxysmal nocturnal hemoglobinuria (PNH), a rare clonal hematopoietic disorder. While PNH is classically associated with venous thrombosis, arterial thromboembolic events are uncommon and may obscure the diagnosis, especially in young patients without underlying vascular risk factors. Clinicians should maintain awareness of PNH's variable presentation and its potential to masquerade as more common thrombotic or autoimmune conditions. Early recognition and appropriate therapy can prevent further complications and improve patient outcomes. This case contributes to the growing recognition of arterial events as a possible manifestation of PNH and reinforces the value of comprehensive diagnostic evaluation in cases of recurrent stroke without an obvious cause.